As you can see in the scheme, I make that to be precisely 3.3V power. I think that 2.3-2.4V is normal for it will report a "power-off or low voltage" error instead of "no device".
Or.. Do you think that the decoupling capacitor on the Jtag connector is a reason?

I haven't used JTAG in decades, but I'm guessing it should show the exact board voltage ± 0.1 volt, like my PDI connection. The programmer/debugger must know the board voltage so it knows the correct signal voltage to send to the board.

I use a Jtag-Jumper wire to connect the connector as the AVR one. However, the reading is 1.4V. Even if I connect the Vcc and GND of the Jtag connector to the precise 3.3V and GND on the board, the reading is also 1.4V... As the result, the green light of the ICE is not on and an error message 'low voltage' is shown during programming. I even connect a pull-up resistor on TCK according to the EVK1101 schematic but it doesn't work.